Today, communication of data and speech in communication networks is commonly distributed circuit switched (CS) or packet switched (PS). In CS communication, a communication channel is reserved for the communication. In PS, on the other hand, communication of data or speech is divided in packets where the packets may be distributed various ways from a sending party to a receiving party, e.g. in shared communication resources. Moreover, in PS, various buffering steps are arranged at the communication parties and between them. The buffering steps achieve the receiving party to arrange the received packets and recover the data sent from the sending party. Lost packets, or packets affected by noise, can be identified and requested to be resent from the sending party. Thereby, PS communication is less sensitive to disturbances, but is instead delayed by various buffering steps and recovering procedures. In CS, the communication is not delayed, but is instead more sensitive for disturbances.
In this description, the term “User Equipment” (UE) will be used to denote any suitable communication terminal adapted to communicate with a base station. A UE may be implemented as a mobile phone, a FDA (Personal Digital Assistant), a handheld computer, a laptop computer, etc. In communication networks where both CS data and PS data are communicated, e.g. WCDMA (Wideband Code Division Multiple Access), a “base station” may be implemented as a NodeB, a repeater, etc.
An example of a cellular communication network where both CS communication and PS communication of data are applied will now be described with reference to FIG. 1, and according to the prior art.
In a communication network 100 a Radio Network Controller (RNC) 102 is arranged to control communication of data which is communicated in the network 100. The communication network 100 comprises also a radio base station 104 which is arranged to communicate user data with various UEs 106, 108, 110. The base station 104 communicates CS based user data with the UE 106, and PS based user data with the UEs 108 and 110. The UEs 108 and 110 are illustrated as different types of UEs, but both of them are communicating PS data. In the communication network 100, PS data and CS data share the same transmission resources, i.e. the UEs 106, 108, and 110 are located in the same cell. In this description the terms “CS data” and “PS data” will be used to denote user data which is communicated circuit switched, and user data which is communicated packet switched, respectively.
Real time services, such as voice, require timely reception of data but are usually robust to handle some level of data errors. Historically, CS is the typical choice for communication in real time, e.g. voice communication. For other services, where it is more important that all data is correctly communicated, which are less sensitive to delays, e.g. data communication, e-mail, FTP, etc., PS is the typical alternative. Typically, CS services are prioritised over PS services in the communication network. The PS services can therefore be used to fill out and optimise the use of the communication network.
However, with the emergence of communication services, e.g. heavy data usage of mobile broadband, there could be PS services which have to be prioritised over CS services, e.g. PS based emergency services, control signalling related to PS, etc. It might not be that attractive to limit the use of CS services to be prepared to provide additional PS services in the communication network. Terminating CS services is not either attractive to the service providers and the CS users. The providers are then not able to reliably deliver the service, and the CS users perceive abruptly broken services annoying.
It is thus a problem to provide reliable communication conditions for communication of PS data in combined communication networks for CS data and PS.